In such lamps, the illuminant is a source of heat that has to be cooled down by means of the respective cooling device, which is advantageous or even necessary in particular with regard to the use in potentially explosive areas. The illuminant is usually disposed in close proximity to the cooling device or on the cooling device. A cooling body with appropriate cooling fins can for example be used as a cooling device.
In recent times, for example LEDs (light-emitting diodes) have been frequently used as illuminants. In contrast to the illuminants that have been commonly used up to present, they are more effective with regard to a respective transformation of the energy used into visible light. However, also in these LEDs, only a maximum of 30% of the energy used is transformed into visible light. Especially in case of such illuminants, it is though necessary for them to be cooled sufficiently as their lifespan, light yield or also their color emission would otherwise be negatively influenced in case of too high temperatures. In addition, the rule that in case of temperatures of 120° C. or more, a respective semiconductor crystal of the LED will be damaged, which will lead to permanent impairment of lifespan, light color, light yield or the like, applies.
The cooling systems used up to present are fastened within the lamp enclosure in a way that on one hand a respective heat transmission from the illuminant to the cooling device can take place and on the other hand the alignment of the illuminant in relation to the appropriate light emission opening is ensured. However, appropriate reflection devices can be used as aids for this purpose.
Experience has shown that both the cooling device as well as the respective points of the lamp enclosure on which the cooling device is fastened have manufacturing tolerances so that a relevant heat transmission contact between the cooling device and the lamp enclosure for dissipation of the heat to the enclosure and finally into the environment is impaired. This is partially compensated through additional application of a heat-conducting paste or the like.